Polyesters are often used to manufacture shaped articles for use in a wide range of applications, including films, sheets, profiles, bottles, and the like. The most commonly used polyesters are based on terephthalic or isophthalic acid monomers and include, for example, poly(ethylene terephthalate) (“PET”), poly(1,4-butylene terephthalate) (“PBT”), poly(cyclohexylenedimethylene terephthalate) (“PCT”), and their copolyesters. These polyesters are inexpensive, widely available and, because of their aromatic content, have a high glass transition temperature (Tg), which gives a shaped article thermal resistance, stiffness (i.e. modulus) and toughness. Recently, much of the emphasis in the polyester arts has been to develop polyesters with higher glass transition temperatures by incorporating greater aromaticity into the polymer (e.g. liquid crystal polyesters, PEN). For certain applications, however, these aromatic polyesters are not acceptable, particularly those applications in which the article requires UV or chemical resistance, good light transmission, and/or a “soft feel”. The term “soft feel” refers to tactile properties similar to those found in polyolefins in which the material is soft to the touch, but still retains structural integrity, elasticity and resiliency. For example, shaped articles prepared from these aromatic polyesters often require a protective cap layer to guard against UV and chemical exposure. In addition, the high modulus of aromatic polyesters makes them unacceptable for use in soft-feel and “low noise” applications, except where a high level of plasticizer is added.
By contrast, aliphatic and cycloaliphatic polyesters typically have good UV and chemical resistance and a lower modulus in comparison to aromatic polyesters. These polyesters, however, have undesirably low glass transition temperatures making them unfit for many applications. For example, many aliphatic and cycloaliphatic type polyesters have glass transition temperatures below room temperature which results in an excessively soft and rubbery polymer with little or no structural integrity. In contrast, aliphatic and cycloaliphatic polyesters with glass transition temperatures above room temperature are glassy but lack adequate toughness and thermal resistance in comparison to aromatic polyesters because their Tg is still too low. Thus, shaped articles prepared from aliphatic and cycloaliphatic polyesters are often inadequate for many applications such as, for example, wall coverings, fibers, packaging, labels, and soft films. Some examples of various cycloaliphatic polyester compositions and their applications are described in U.S. Pat. Nos. 5,306,785; 5,859,119; 5,907,026; 6,011,124; 5,486,562; 5,907,026; 4,665,153; 6,084,055; 6,455,664; and 6,136,441; U.S. Patent Application Publication No. 2003/0030172 A1; European Patent Application No. 0 902 052 A1; and in PCT Application No.'s WO 93/04124 and WO 02/31020 A2.
Other non-aromatic polyesters do not cure these deficiencies and present additional shortcomings when used for shaped articles. For example, polyester elastomers such as, for example, PCCE copolyesterethers (a copolymer of 1,4-cyclohexane-dicarboxylic acid, 1,4-cyclohexanedimethanol, and polytetramethylene glycol (available under the trademark ECDEL® polyester from Eastman Chemical Company) have many desirable properties, such as the toughness and UV/chemical resistance mentioned above. They also have a soft feel, but are too soft and rubbery, and lack the thermal resistance needed to be used in many structural applications. Furthermore, because of these rubber-like properties in combination with their slow crystallization characteristics, extruded films and fibers from these polyester elastomers tend to stick to take up rolls or spinning guides during extrusion. Fluoropolymer and matte rolls/tooling tend to alleviate the sticking problem but such materials are expensive and require dedicated processing lines. Thus, it would be desirable to prepare shaped articles such as, for example, bottles, films, sheets, profiles, fibers, tubes, and molded objects, that have good UV and chemical resistance while simultaneously retaining strength, toughness, thermal resistance, and soft feel characteristics. Such articles would have applications in wall coverings, bottles, soft films, packaging, labels, and fibers.